JPH1060427A - Organic el element produced by using coumarin derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject element having suppressed increase in driving voltage, lowering of luminescent intensity, leakage of current, etc., having high reliability and especially emitting red light having high intensity by using a coumarin derivative having a specific structure as a component of an organic compound layer. SOLUTION: This EL, element has an organic compound layer containing a coumarin derivative of the formula (R1 to R4 are each H or an alkyl; Z is an atomic group necessary for forming a benzene ring or naphthalene ring together with two carbon atoms). The organic compound layer containing the compound of the formula is preferably the luminescent layer. The compound of the formula is preferably doped in the host material of the luminescent layer. The doping concentration is preferably 0.05-1wt.% for getting an element having high luminescence and 1.5-3wt.% for an element having high color purity. The host material doped with the compound of the formula is preferably tris (8- quinolinolato)aluminum. The compound may be used as a dopant in a mixed layer of a hole-injection transfer compound and an electron transfer compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (EL) device, and more particularly, to a device that emits light by applying an electric field to a thin film made of an organic compound.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin film containing a fluorescent organic compound is sandwiched between a cathode and an anode. This is an element that emits light by utilizing light emission (fluorescence / phosphorescence) when the exciton is deactivated.

[0003] The features of the organic EL element are that it can emit a high-luminance surface light of about 100 to 100000 cd / m ² at a low voltage of about 10 V, and emit light from blue to red by selecting the type of fluorescent substance. Is possible.

[0004] On the other hand, the problems of the organic EL element are that the light emission life is short, the storage durability and the reliability are low. Non-uniformity occurs, which causes deterioration of the charge injection capability of the device, short-circuiting, and dielectric breakdown.Especially, when a low molecular compound having a molecular weight of 500 or less is used, crystal grains appear and grow, and the film properties are remarkably deteriorated.
Further, even if the interface of ITO or the like is rough, remarkable crystal grains appear and grow, which causes a decrease in luminous efficiency and a leakage of current, resulting in no light emission. It also causes a dark spot which is a partially non-light emitting portion. )

Oxidation and exfoliation of the cathode (Na, Mg, Li, Ca, K, Al, etc. have been used as metals having a small work function in order to facilitate electron injection. In particular, when a film is formed by spin coating using a polymer compound or the like, the solvent and decomposition products remaining on the electrode may be reduced. Promotes the oxidation reaction of the electrode, and the electrode is peeled off to generate a partial non-light emitting portion.)

Low luminous efficiency and large amount of heat generation (Since current flows in the organic compound, the organic compound must be placed under a high electric field strength, and it cannot escape heat generation.
Due to the heat, the element is deteriorated or broken due to melting, crystallization, thermal decomposition, etc. of the organic compound. )

[0007] Photochemical and electrochemical changes of the organic compound layer can be mentioned.

In particular, the organic EL emitting red light has a short life,
No high brightness was obtained. For example, Japanese Patent Application Laid-Open No. 3-792 discloses an electroluminescent element in which a phosphor light emitting layer composed of a phosphor thin film containing a coumarin compound is disposed, and a device emitting red light is disclosed in Example 2 thereof. I have. However, the electroluminescent device shown here has low light emission luminance and is not practical.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide various luminescent colors having high reliability and luminous efficiency, particularly by using optical and electronic functional materials having little physical change, photochemical change and electrochemical change. Organic E with red emission color
This is to realize an L element. In particular, using an organic thin film formed by depositing a compound with a high molecular weight by vapor deposition, high reliability that suppresses the rise of driving voltage and the decrease in brightness, the leakage of current, and the appearance and growth of non-light emitting parts when driving the device Another object is to realize a high-luminance light-emitting element with high red purity.

[0010]

This and other objects are achieved by the present invention which is defined below as (1) to (7). (1) An organic EL device having at least one organic compound layer, wherein at least one organic compound contains a coumarin derivative represented by the following formula (I).

[0011]

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[In the formula (I), R ₁ , R ₂ , R ₃ and R
₄ represents a hydrogen atom or an alkyl group, which may be the same or different. Z represents an atomic group necessary for forming a benzene ring or a naphthalene ring together with two carbon atoms. (2) The organic EL device according to the above (1), wherein the organic compound layer containing the coumarin derivative is a light emitting layer. (3) The organic EL device according to (2), wherein the coumarin derivative is doped into a host material. (4) The organic EL device according to (3), wherein the host material is a quinolinonato metal complex. (5) The organic EL device according to the above (2), wherein the light emitting layer is a mixed layer of at least one kind of hole injecting and transporting compound and at least one kind of electron injecting and transporting compound. (6) The above (2), wherein the light emitting layer is sandwiched between at least one layer of hole injecting and / or hole transporting and at least one layer of electron injecting and / or electron transporting. The organic EL device according to any one of (1) to (5). (7) The organic EL according to any one of (1) to (6) above, wherein a color filter and / or a fluorescence conversion filter is arranged on the light extraction side, and light is extracted through the color filter and / or the fluorescence conversion filter.
element.

[0013]

In the organic EL device of the present invention, since the coumarin derivative represented by the formula (I) is used in the light emitting layer, red light and high luminance of about 1000 cd / m ² or more can be stably obtained. Further, by selecting a host material having high heat resistance and durability, stable driving is possible even at an element current density of about 100 mA / cm ² .

Since the vapor-deposited film of the above compound is in a stable amorphous state, the physical properties of the thin film are improved and uniform light emission without unevenness is possible. It is stable in the atmosphere for more than one year and does not crystallize.

Further, the organic EL device of the present invention emits light efficiently at a low driving voltage.

The maximum emission wavelength of the organic EL device of the present invention is about 500 to 700 nm. Note that among the coumarin derivatives represented by the formula (I), R ₁ = R ₂ = R ₃ = R
Compounds in which the ring completed by ₄ = CH ₃ , Z is a benzene ring are described in “Satsuki, Mitekura, Mori, Yasui, Proceedings of the 70th Annual Meeting of the Chemical Society of Japan, P30 (1996)”. Thus, it has been shown that it can be applied to a photopolymerization sensitized system. However, there is no description as to the use in an organic compound layer of an organic EL device as in the present invention.

[0017]

Embodiments of the present invention will be described below in detail. The organic EL device of the present invention has the formula (I)
Has at least one organic compound layer containing a coumarin derivative represented by

Describing the formula (I), the formula (I)
Wherein R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom or an alkyl group, which may be the same or different. As the alkyl group represented by R _{1 to} R ₄ ,
It preferably has 1 to 6 carbon atoms, and may be linear or branched, and may be cyclic in some cases. Further, it may have a substituent. R _{1 to} R
Specific examples of the alkyl group represented by ₄ include a methyl group, an ethyl group, an (n-, i-) propyl group, and a (n-, i
-, S-, t-) butyl group, n-pentyl group, isopentyl group, t-pentyl group, 1-methylbutyl group, n-hexyl group and the like. The alkyl group represented by R _{1 to} R ₄ preferably has 1 to 6 carbon atoms in total. R ₁ ~
R ₄ is preferably a methyl group or the like, and R _{1 to} R ₄ are usually the same.

Z represents an atomic group necessary for forming a benzene ring or a naphthalene ring together with two carbon atoms in the imidazole ring, and these benzene ring and naphthalene ring may further have a substituent. Specific examples of these substituents will be described later. When the ring formed by Z is a naphthalene ring, when a benzimidazole ring containing an imidazole ring is considered as a basic component, the condensed position of a benzene ring in this benzimidazole ring may be any, and 4,5th, 5,6th,
It may be at any of positions 6 and 7 (see the following structural formula).

[0020]

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Among the compounds of the formula (I), the compounds of the following formula (Ia) are preferred.

[0022]

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In the formula (Ia), R _{1 to} R ₄ have the same meanings as in the formula (I), and R ₅ , R ₆ , R ₇ and R ₈ each represent a hydrogen atom, an alkyl group (for example, a methyl group) , An ethyl group, a butyl group, etc.), an alkoxy group (eg, a methoxy group, etc.), an aryl group (eg, a phenyl group, (o-, m
—, P-) tolyl group, etc.), an aryloxy group (eg, a phenoxy group), a substituted amino group (eg, a diphenylamino group), a heterocyclic group (eg, a pyridyl group, a thienyl group). R _{5 to} R ₈ are preferably a hydrogen atom, an aryl group or the like.

R ₅ and R ₆ , R ₆ and R ₇ or R ₇
And R ₈ may be bonded to each other to form a benzene ring, and forming a benzene ring in this manner is also preferable in some cases. The benzene ring thus formed may further have a substituent. In this case, examples of the substituent include those similar to the substituents represented by R _{5 to} R ₈ .

Specific examples of the coumarin derivative represented by the formula (I) are shown below, but the present invention is not limited to these. Examples of the compound include R _{1 to} R ₈ in the formula (Ia).
Are shown. Ph represents a phenyl group.

[0026]

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The coumarin derivative represented by the formula (I) is described in German Patent Publication No. 2253538 [Ger. Offen. 2253538 (Ger. Ap).
pl.1972) W. Mach, D. Augart, H. Scheuermann] and the like.

The coumarin derivatives of the formula (I) may be used alone or in combination of two or more.

The organic EL device of the present invention has at least one organic compound layer, and at least one organic compound layer contains a coumarin derivative represented by the formula (I). FIG. 1 shows a configuration example of the organic EL element of the present invention. The organic EL device 1 shown in FIG. 1 has an anode 3, a hole injection / transport layer 4, a light emitting layer 5, an electron injection / transport layer 6, and a cathode 7 on a substrate 2 in order. It is something to take out. A color filter film 8 and a fluorescence conversion filter film 9 are provided between the substrate 2 and the anode 3 from the substrate 2 side to control the emission color. Further, the organic EL element 1 is provided with a sealing layer 10 that covers these layers 4 to 6, 8, and 9 and the electrodes 3 and 7. In the casing 11, the whole of which is integrated with the glass substrate 2, Are located in A gas or liquid 12 is filled between the sealing layer 10 and the casing 11. The sealing layer 10 is formed of a resin such as Teflon, and the material of the casing 11 may be glass or the like, and can be joined to the substrate 2 or the like with a photocurable resin adhesive or the like. As the gas or liquid 12, air, a halogen compound (particularly, a fluorine compound) or the like is used.

The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.
The hole injection / transport layer has a function of facilitating the injection of holes from the anode, a function of transporting holes, and a function of blocking electrons.The electron injection / transport layer facilitates injection of electrons from the cathode. These layers have the function of transporting electrons, the function of transporting electrons, and the function of blocking holes.These layers increase and confine holes and electrons injected into the light emitting layer, optimize the recombination region, and improve light emission. Improve efficiency. The hole injecting and transporting layer and the electron injecting and transporting layer, considering the height of each function of hole injection, hole transport, electron injection, and electron transport of the compound used for the light emitting layer,
Provided as needed. For example, when the compound used for the light-emitting layer has a high hole-injection-transport function or an electron-injection-transport function, the light-emitting layer may be provided without the hole-injection-transport layer or the electron-injection-transport layer. It can be configured to also serve as a transport layer. In some cases, neither the hole injection transport layer nor the electron injection transport layer may be provided. In addition, the hole injection / transport layer and the electron injection / transport layer may be separately provided in a layer having an injection function and a layer having a transport function.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited, and vary depending on the forming method.
It is preferable that the thickness be 0 to 200 nm.

The thickness of the hole injecting and transporting layer and the thickness of the electron injecting and transporting layer depend on the design of the recombination and light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. . When the injection layer and the transport layer for electrons or holes are separated from each other, it is preferable that the injection layer has a thickness of 1 nm or more and the transport layer has a thickness of 20 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 100 nm for the injection layer and 100 nm for the transport layer.
It is about 0 nm. Such a film thickness is the same when two injection / transport layers are provided.

Further, by controlling the film thickness in consideration of the carrier mobility and carrier density (determined by ionization potential and electron affinity) of the combined light emitting layer, electron injection transport layer and hole injection transport layer, recombination can be achieved. It is possible to freely design the region and the light emitting region, and it is possible to design the light emission color, control the light emission luminance and light emission spectrum by the interference effect of both electrodes, and control the spatial distribution of light emission.

The coumarin derivative of the formula (I) is a relatively neutral compound and is preferably used for the light emitting layer. However, the coumarin derivative is also applicable to a hole injection transport layer and an electron injection transport layer.

In the case where the coumarin derivative of the formula (I) is used in the light emitting layer, the coumarin derivative of the formula (I) is used in an amount of 10
It is preferable to be not more than wt%. Therefore, it is preferable to use the host material of the light emitting layer by doping it. In such a case, in practice, the doping concentration may be determined according to the required luminance and color purity. In particular, an element having a high luminance can be obtained at 1 wt% or less, and an element having a high color purity can be obtained at 1.5 wt% or more. Can be

From the above, in order to obtain a high-luminance element, 0.01 to 1.4 wt%, particularly 0.05 to 1 wt%
1.5 to 10% by weight to obtain a device with high color purity,
In particular, the content is preferably 1.5 to 3% by weight.

In the present invention, a fluorescent material other than the coumarin derivative of the formula (I) can be used in the light emitting layer. Examples of such a fluorescent material include, for example, JP-A-63-264.
No. 692, for example, at least one compound selected from compounds such as quinacridone, rubrene, and styryl dyes. Also, quinoline derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof as a ligand, such as tris (8-quinolinolato) aluminum, tetraphenylbutadiene, anthracene, perylene, coronene, and 12-phthaloperinone derivatives. Further, phenylanthracene derivatives described in JP-A-8-12600, JP-A-8-12969
And the like.

The host material doped with the coumarin derivative of the formula (I) is preferably a quinoline derivative, more preferably a quinolinonato metal complex having 8-quinolinol or a derivative thereof as a ligand, particularly preferably an aluminum complex. At this time, the derivative of 8-quinolinol includes 8-quinolinol obtained by substituting a halogen atom, an alkyl group, or the like, and a derivative obtained by condensing a benzene ring. Such an aluminum complex is disclosed in, for example, JP-A-63-264692.
JP-A-3-255190, JP-A-5-70733
JP-A-5-258859, JP-A-6-21587
No. 4 and the like.

Specifically, first, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum Oxide, tris (8-quinolinolato) indium,
Tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-
8-quinolinolato) gallium, bis (5-chloro-8-
Quinolinolato) calcium, 5,7-dichloro-8-quinolinolatoaluminum, tris (5,7-dibromo-
8-hydroxyquinolinolato) aluminum, poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane], and the like.

In addition to 8-quinolinol or its derivative, an aluminum complex having another ligand may be used, such as bis (2-methyl-
8-quinolinolato) (phenolato) aluminum (III)
, Bis (2-methyl-8-quinolinolato) (ortho-
Cresolato) aluminum (III), bis (2-methyl-
8-quinolinolato) (meth-cresolate) aluminum
(III), bis (2-methyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl-8-quinolinolato) (ortho-phenylphenolate)
Aluminum (III), bis (2-methyl-8-quinolinolato) (meth-phenylphenolato) aluminum (II
I), bis (2-methyl-8-quinolinolato) (para-
Phenylphenolato) aluminum (III), bis (2-
Methyl-8-quinolinolato) (2,3-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-dimethylphenolato) aluminum (III), bis (2-methyl- 8-quinolinolato)
(3,4-dimethylphenolato) aluminum (III),
Bis (2-methyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III) ), Bis (2-methyl-8)
-Quinolinolato) (2,6-diphenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,4,6-triphenylphenolato) aluminum (III), bis (2-methyl- 8-quinolinolato)
(2,3,6-trimethylphenolato) aluminum (I
II), bis (2-methyl-8-quinolinolato) (2,
3,5,6-tetramethylphenolato) aluminum (I
II), bis (2-methyl-8-quinolinolato) (1-naphthrat) aluminum (III), bis (2-methyl-8
-Quinolinolato) (2-naphthrat) aluminum (II
I), bis (2,4-dimethyl-8-quinolinolato)
(Ortho-phenylphenolato) aluminum (III),
Bis (2,4-dimethyl-8-quinolinolato) (para-
Phenylphenolato) aluminum (III), bis (2,
4-dimethyl-8-quinolinolato) (meta-phenylphenolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2 4-dimethyl-8
-Quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III), bis (2-methyl-4-ethyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl) -4-methoxy-8-quinolinolato) (para-phenylphenolato) aluminum (III), bis (2-methyl-5-cyano-8-quinolinolato) (ortho-cresolato) aluminum (III),
Bis (2-methyl-6-trifluoromethyl-8-quinolinolato) (2-naphthrat) aluminum (III);

In addition, bis (2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2-
Methyl-8-quinolinolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) aluminum
(III) -μ-oxo-bis (2,4-dimethyl-8-quinolinolato) aluminum (III), bis (4-ethyl-
2-methyl-8-quinolinolato) aluminum (III)-
μ-oxo-bis (4-ethyl-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-4
-Methoxyquinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-4-methoxyquinolinolato)
Aluminum (III), bis (5-cyano-2-methyl-
8-quinolinolato) aluminum (III) -μ-oxo-
Bis (5-cyano-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) -μ
-Oxo-bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) and the like.

Among these, in the present invention, it is particularly preferable to use tris (8-quinolinolato) aluminum.

The light-emitting layer using the coumarin derivative of the formula (I) may be used in combination with at least one of the above-mentioned host materials and at least one or more hole-injecting and transporting compounds and at least one or more electron-injecting and transporting compounds. It is preferable that the compound of the formula (I) is contained as a dopant in the mixed layer. The content of the coumarin derivative of the formula (I) in such a mixed layer may be the same as described above, depending on the purpose and the like.

In the mixed layer, a carrier hopping conduction path is formed, so that each carrier moves in a material having a polarity predominant, and injection of a carrier having the opposite polarity is less likely to occur, so that the organic compound is less likely to be damaged. However, by incorporating the coumarin derivative of the formula (I) into such a mixed layer, the emission wavelength characteristics of the mixed layer itself can be changed, and the emission wavelength can be increased. And the emission intensity is increased, and the stability of the device is improved.

The hole injecting and transporting compound and the electron injecting and transporting compound used in the mixed layer may be selected from the following compounds for the hole injecting and transporting layer and the compounds for the electron injecting and transporting layer, respectively. Above all, as the electron injecting and transporting compound, it is preferable to use a quinoline derivative, furthermore a metal complex having 8-quinolinol or a derivative thereof as a ligand, particularly tris (8-quinolinolato) aluminum.

The mixing ratio in this case depends on the carrier mobility, but the weight ratio of the hole injecting / transporting compound / electron injecting / transporting compound is 30/70 to 70/30, more preferably 40/6.
0 to 60/40, especially about 50/50).

Further, the thickness of the mixed layer is preferably less than the thickness of the organic compound layer from the thickness corresponding to one molecular layer, more preferably from 1 to 85 nm.
Further, the thickness is preferably 5 to 60 nm, particularly preferably 5 to 50 nm.

As a method of forming the mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are approximately the same or very close, they are mixed in advance in the same evaporation board. Alternatively, it can be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may exist in an island shape. The light-emitting layer is generally formed to a predetermined thickness by vapor-depositing an organic fluorescent substance or by dispersing and coating the resin in a resin binder.

In the present invention, an electron injecting and transporting layer which is an electron injecting and / or transporting layer may be provided. The electron injecting / transporting layer includes a quinoline derivative such as an organometallic complex having 8-quinolinol or its derivative such as tris (8-quinolinolato) aluminum as a ligand, an oxadiazole derivative, a perylene derivative, a pyridine derivative, and a pyrimidine derivative. , Quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and the like. The electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injecting and transporting layer may be formed by vapor deposition or the like, similarly to the light emitting layer.

When the electron injecting and transporting layer is provided separately for the electron injecting layer and the electron transporting layer, a preferable combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having a higher electron affinity value from the cathode side, and it is preferable to provide an electron injection layer in contact with the cathode and an electron transport layer in contact with the light emitting layer. The relationship between the electron affinity and the stacking order is the same when two or more electron injection / transport layers are provided.

In the present invention, a hole injecting and transporting layer which is a hole injecting and / or transporting layer may be provided. Various organic compounds described in JP-A-63-295695, JP-A-2-191694, JP-A-3-792, etc., such as aromatic tertiary amines and hydrazones, are used in the hole injecting and transporting layer. Derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having an amino group, polythiophenes, and the like can be used. These compounds may be used as a mixture of two or more kinds, or may be used by laminating. Among these compounds, N, N'-bis-4 (-N- (m-biphenyl) -N-phenyl-4'-aminobiphenyl)-
N, N'-diphenyl-1,1'-biphenyl-4,
4'-diamine, N, N, N ', N'-tetrakis (-
m-biphenyl) -1,1'-diphenyl-4,4'-
Diamine, N, N'-bis (4-methylphenyl)-
N, N'-diphenyl-1,1'-biphenyl-4,
Triphenyldiamine (TPD) derivatives such as 4 'diamine are preferred. For details of these compounds, see JP-A-63-295695, JP-A-5-234681, and
P0650955A1 (Japanese Patent Application No. 7-43564).

When the hole injecting and transporting layer is provided separately as a hole injecting and transporting layer, a preferable combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having the smaller ionization potential in order from the anode (ITO or the like) side, and it is preferable to provide a hole injection layer in contact with the anode and a hole transport layer in contact with the light emitting layer. It is preferable to use a compound having good thin film properties on the anode surface. The relationship between the ionization potential and the stacking order is the same when two or more hole injection / transport layers are provided. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In the case of forming an element, a thin film of about 1 to 10 nm can be made uniform and pinhole-free because of the use of vapor deposition, so that the hole injection layer has a small ionization potential and has absorption in the visible part. Even when such a compound is used, it is possible to prevent a change in the color tone of the emission color or a decrease in efficiency due to reabsorption.

In the present invention, the organic compound layer may contain a singlet oxygen quencher. Examples of such a quencher include rubrene, a nickel complex, diphenylisobenzofuran, and a tertiary amine. Particularly in the hole injection transport layer, the hole injection layer or the hole transport layer,
N, N'-bis-4 (-N- (m-biphenyl) -N-
Phenyl-4′-aminobiphenyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine;
N, N, N ', N'-tetrakis (3-biphenyl)-
1,1′-diphenyl-4,4′-diamine, N, N ′
It is preferable to use a rubrene in combination with a TPD derivative such as -bis (4-methylphenyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine. Preferably, it is 1 to 10% by weight of the TPD derivative. For such rubrene, E
Reference can be made to the description of P0650955A1 (Japanese Patent Application No. 7-43564).

In the present invention, a material having a small work function, for example, Li, Na, Mg, Al, Ag, I, is used for the cathode.
It is preferable to use n or an alloy containing one or more of these. The cathode preferably has fine crystal grains, and particularly preferably has an amorphous state. The thickness of the cathode is preferably about 10 to 1000 nm.

In order for the organic EL element to emit light from the surface, at least one of the electrodes must be transparent or translucent, and the material of the cathode is limited as described above. Is preferably determined so as to be 80% or more. Specifically, for example, ITO, SnO ₂ , Ni, Au, Pt, P
d, It is preferable to use polypyrrole doped with a dopant for the anode. The thickness of the anode is 10 to 50.
Preferably, it is about 0 nm. Further, it is necessary that the driving voltage is low in order to improve the reliability of the element,
10 to 30Ω / □ or 10Ω / □ is preferable.
The following (usually 0.1 to 10 Ω / □) ITO may be mentioned.

The material of the substrate is not particularly limited, but in the illustrated example, a transparent or translucent material such as glass or resin is used in order to extract emitted light from the substrate side. Further, as shown in the figure, the color of emitted light may be controlled by using a color filter film, a fluorescence conversion filter film containing a fluorescent substance, or a dielectric reflection film as shown in the drawing.

When an opaque material is used for the substrate, the stacking order shown in FIG. 1 may be reversed.

In the present invention, by using the coumarin derivative of the formula (I) in the light emitting layer, the maximum light emission wavelength λmax is 50
Emission of 0-700 nm, especially red light of 580-640 nm, is obtained. The CIE chromaticity coordinates at this time are NTS
Red color reproduction of C standard (x = 0.67, y = 0.33)
Or the red color purity of the current CRT (x = 0.6
3, y = 0.34) or more is preferable.

The above chromaticity coordinates can be measured by a general chromaticity measuring device. In the present invention, the measurement is performed using a measuring machine BM-7, SR-1 manufactured by Topcon Corporation.

In the present invention, λ max and emission of x and y values of CIE chromaticity coordinates may be obtained by providing a color filter film or a fluorescence conversion filter film.

As the color filter film, a color filter used in a liquid crystal display or the like may be used, but the characteristics of the color filter are adjusted according to the light emitted from the organic EL to optimize the extraction efficiency and color purity. It should just be. In addition, it is preferable to use a color filter that can cut light having a short wavelength (wavelength of 560 nm or less) such that the EL element material or the fluorescence conversion layer absorbs light, thereby improving the light resistance and display contrast of the element. By using such a color filter, preferable x and y values can be obtained in CIE chromaticity coordinates. The thickness of the color filter film may be about 1 to 10 μm.

Further, an optical thin film such as a derivative multilayer film may be used instead of the color filter.

The fluorescence conversion filter film absorbs EL light and emits light from the phosphor in the fluorescence conversion film to convert the color of emitted light. It is formed from three.

As the fluorescent material, basically, a material having a high fluorescence quantum yield may be used, and it is desirable that the material has strong absorption in the EL emission wavelength region. Specifically, a fluorescent substance having an emission maximum wavelength λmax of the fluorescence spectrum of 580 to 640 nm and a half width of the spectrum near λmax of 10 to 60 nm is preferable. Actually, dyes for laser are suitable, and rhodamine-based compounds, perylene-based compounds, cyanine-based compounds, phthalocyanine-based compounds (including subphthalocyanine, etc.), naphthalimide-based compounds, condensed-ring hydrocarbon-based compounds, condensed-heterocycles Compounds, styryl compounds and the like may be used.

As the binder, basically, a material which does not extinguish the fluorescence may be selected, and a binder which can be finely patterned by photolithography, printing or the like is preferable.
Further, a material that does not suffer damage during the deposition of ITO is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not extinguish the fluorescence of the fluorescent material may be selected.

By using such a fluorescence conversion filter, preferable x and y values can be obtained in CIE chromaticity coordinates. Further, the thickness of the fluorescence conversion filter film is 1-1.
It may be about 0 μm.

In the present invention, a color filter film and a fluorescence conversion filter film may be used in combination as shown in the illustrated example. Preferably, a color filter film that cuts light of a specific wavelength is disposed on the side from which emitted light is extracted. I just need.

It is preferable to provide a protective film (overcoat) on the color filter film or the fluorescence conversion filter film. The material of the protective film may be resin, glass, or the like, and a material that can prevent damage to the filter film and does not cause a problem in a subsequent process may be selected, and has a thickness of about 1 to 10 μm. By providing the protective film, damage to the filter film can be prevented, and the surface can be flattened.

Commercially available products can be used for the color filter film, the fluorescence conversion filter film, and the protective film as they are.
(Sputtering, CVD, etc.), or an electrolytic polymerization method.

Next, a method for manufacturing the organic EL device of the present invention will be described.

The cathode and anode are preferably formed by a vapor phase growth method such as a vapor deposition method or a sputtering method.

For forming the hole injecting and transporting layer, the light emitting layer and the electron injecting and transporting layer, it is preferable to use a vacuum evaporation method since a uniform thin film can be formed. When a vacuum deposition method is used, a homogeneous thin film having an amorphous state or a crystal grain size of 0.1 μm or less (the lower limit is usually about 0.001 μm) can be obtained. If the crystal grain size exceeds 0.1 μm, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the charge injection efficiency is significantly reduced.

The conditions for vacuum deposition are not particularly limited.
It is preferable that the degree of vacuum be 0 ^-3 Pa (10 ^-5 Torr) or less, and the deposition rate be about 0.1 to 1 nm / sec. Also,
It is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained. Further, the driving voltage of the element can be reduced.

In the case where a plurality of compounds are contained in one layer in the case where a vacuum evaporation method is used for forming each of these layers, it is preferable to individually control the temperature of each boat containing the compounds and co-evaporate them. After that, vapor deposition may be performed.
In addition, a solution coating method (spin coating, dip, casting, etc.) such as a Langmuir-Blodget (LB) method can also be used. In the solution coating method, each compound may be dispersed in a matrix material such as a polymer.

The organic EL device of the present invention is generally used as a DC-driven EL device, but can be driven by AC or pulse. The applied voltage is usually 2 to 20
V.

[0077]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention. <Example 1> A glass substrate having a 100 nm thick ITO transparent electrode (anode) was ultrasonically cleaned using a neutral detergent, acetone and ethanol, pulled up from boiling ethanol, dried, and washed with UV ozone. The pressure was reduced to 1 × 10 ⁻⁶ Torr or less by fixing to a substrate holder of a vapor deposition device.

Next, the following 4,4′4 ″ -tris (-
N-(-3-methylphenyl) -N-phenylamino)
Triphenylamine (MTDATA) was distilled at a distillation rate of 2 nm /
The film was deposited to a thickness of 50 nm in sec to form a hole injection layer.

Further, the following N, N'-bis-4-(-
N- (m-biphenyl) -N-phenyl-4′-aminobiphenyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) was deposited at a deposition rate of 2
The film was deposited at a thickness of 20 nm at a rate of nm / sec to form a hole transport layer.

Then, Exemplified Compound No. 1 and the following tris (8-quinolinolato) aluminum (A1Q3) were mixed at a weight ratio of 0.5: 100 and a distillation rate of 0.5 nm / sec.
Was deposited to a thickness of 10 nm to form a light emitting layer.

[0081]

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[0082]

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[0083]

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Next, while maintaining the reduced pressure, tris (8-quinolinolato) aluminum was deposited as an electron injecting and transporting layer to a thickness of 10 nm at a deposition rate of 0.2 nm / sec.

Further, while maintaining the reduced pressure state, the MgAg
(Weight ratio 10: 1) at a distillation rate of 0.2 nm / sec.
A cathode was formed by vapor deposition to a thickness of nm to obtain an EL device.

When a voltage was applied to this EL element to flow a current, the EL element was 28600 cd / m ² at 615 mA / cm ² at 15 V.
Red-orange (maximum emission wavelength λmax = 589 nm, chromaticity coordinate x
= 0.58, y = 0.41), and the light emission was stable in a dry nitrogen atmosphere for 10,000 hours or more. There was no appearance and growth of partial non-light-emitting portions.
The half life of the luminance was 2500 hours (initial luminance: 450 cd / m ² ) at a constant current drive of 10 mA / cm ² .

<Example 2> An element was manufactured in the same manner as in Example 1. However, the ratio of Exemplified Compound No. 1 to tris (8-quinolinolato) aluminum (A1Q3) was 2: 100 by weight.

When a voltage was applied to this EL element to cause a current to flow, a red of 4000 cd / m ² at 16 V, 610 mA / cm ² (maximum emission wavelength λmax = 635 nm, chromaticity coordinates x =
0.64, y = 0.34) was confirmed, and this light emission was stable for 10,000 hours or more in a dry nitrogen atmosphere. There was no appearance and growth of partial non-light-emitting portions.

Example 3 A color filter film was formed on a glass substrate to a thickness of 1 μm, and an overcoat was formed thereon to a thickness of 1 μm. Fuji Hunt CR-2000 was used as a color filter material, and Fuji Hunt CT was used as an overcoat material, and both were formed by coating. The color filter material mainly cuts light having a wavelength of 580 nm or less. On top of this, a thickness of 10
0 nm of ITO was sputtered to produce a red element substrate with an anode. Using this substrate, an element was produced in the same manner as in Example 1.

When a voltage was applied to this EL element to cause a current to flow, it was found that at 15 V, 620 mA / cm ² , 20200 cd / m ² of red (maximum emission wavelength λmax = 614 nm, chromaticity coordinate x =
0.64, y = 0.36) was confirmed, and this light emission was stable for 10,000 hours or more in a dry nitrogen atmosphere. There was no appearance and growth of the partial non-light emitting portion.

Example 4 A red fluorescence conversion film was formed on a glass substrate to a thickness of 5 μm, and an overcoat was formed thereon to a thickness of 1 μm.
m thickness. As the red fluorescence conversion material, a material obtained by dissolving 2 wt% of BASF Lumogen F Red 300 in Fuji Hunt CT-1 was used, and as the overcoat material, Fuji Hunt CT-1 was used, all of which were formed by coating.
The red fluorescence conversion material had an emission maximum wavelength λmax of 620 nm, and the half width of the spectrum near λmax was 30 nm. On this, ITO having a thickness of 100 nm was sputtered to produce a substrate for a red element with an anode. Using this substrate, an element was produced in the same manner as in Example 1.

When a voltage was applied to this EL element to cause a current to flow, the EL element was charged at 11900 cd / m ² at 610 mA / cm ² at 15 V.
Red (emission maximum wavelength λmax = 629 nm, chromaticity coordinate x =
(0.69, y = 0.30) was confirmed, and the luminescence was stable in a dry nitrogen atmosphere for 10,000 hours or more. There was no appearance and growth of partial non-light-emitting portions.

Example 5 A color filter film was formed on a glass substrate to a thickness of 1 μm by application using a CR-2000 manufactured by Fuji Hunt, and a red fluorescence conversion film was formed thereon on a CT-1 manufactured by Fuji Hunt and manufactured by BASF. 2 wt% Lumogen F Red 300
% It is formed to a thickness of 5 μm by coating using the dissolved material,
Furthermore, an overcoat was applied on top of this by CT-1 made by Fuji Hunt.
Was formed to a thickness of 1 μm by coating. On this, ITO having a thickness of 100 nm was sputtered to produce a red element substrate with an anode. Using this substrate, an element was produced in the same manner as in Example 1.

When a voltage was applied to this EL element to cause a current to flow, a red color of 9000 cd / m ² at 615 mA / cm ² at 15 V (maximum emission wavelength λ max = 600 nm, chromaticity coordinate x =
(0.64, y = 0.30) was confirmed, and the luminescence was stable in a dry nitrogen atmosphere for 10,000 hours or more. There was no appearance and growth of partial non-light-emitting portions.

<Example 6> In Example 1, the light-emitting layer was changed to N, N'-bis-4- as a hole injecting / transporting compound.
(-N- (m-biphenyl) -N-phenyl-4'-aminobiphenyl) -N, N'-diphenyl-1,1'-
Biphenyl-4,4'-diamine (TPD) and tris (8-quinolinolato) aluminum (A1Q3) were used as the electron injecting and transporting compound, and the deposition rates were almost the same.
At the same time, Exemplified Compound No. 1 was deposited at a deposition rate of 0.02 nm / sec to form a mixed layer having a thickness of 40 nm. In the mixed layer, TPD: AlQ3: Exemplified Compound No. 1 = 50: 50: 1 (weight ratio). Other than that, the device was manufactured in the same manner as in Example 1, except that the hole injection layer was 50 nm thick, the hole transport layer was 10 nm thick, and the electron injection and transport layer was 40 nm thick.

When a voltage was applied to the EL element to cause a current to flow, the EL element was 29000 cd / m ² at 800 mA / cm ² at 15 V.
Red (emission maximum wavelength λmax = 590 nm, chromaticity coordinate x =
(0.59, y = 0.40) was confirmed, and the luminescence was stable in a dry nitrogen atmosphere for 10,000 hours or more. There was no appearance and growth of partial non-light-emitting portions.

<Example 7> In Example 6, the hole transport layer was replaced with N, N'-bis-(-N- (m-biphenyl)-
N-phenyl-4'-aminobiphenyl) -1,1'-
Biphenyl-4,4'-diamine and rubrene were added to 10
An element was produced in the same manner except that the element was formed by co-evaporation at 0:10 (weight ratio).

When a voltage was applied to the EL element to cause a current to flow, the voltage was 14 V, 615 mA / cm ² , and 41,000 cd / m ^2.
(Emission maximum wavelength λmax = 560 nm, 590 nm, chromaticity coordinates x = 0.57, y = 0.40), and this emission was stable for 10,000 hours or more in a dry nitrogen atmosphere. There was no appearance and growth of partial non-light-emitting portions.

Example 8 In Examples 1 to 7, when Exemplified Compound No. 2 was used instead of Exemplified Compound No. 1, almost the same results were obtained according to the device configuration.

Comparative Example 1 A glass substrate having an ITO transparent electrode (anode) having a thickness of 100 nm was subjected to ultrasonic cleaning using a neutral detergent, acetone and ethanol, pulled up from boiling ethanol, dried, and exposed to UV ozone. After the cleaning, the substrate was fixed to a substrate holder of a vapor deposition apparatus, and the pressure was reduced to 1 × 10 ⁻⁶ Torr.

Then, 4,4′4 ″ -tris (-N-
(3-Methylphenyl) -N-phenylamino) triphenylamine (MTDATA) was deposited at a distillation rate of 2 nm / sec to a thickness of 50 nm to form a hole injection layer.

Further, N, N'-bis-4-(-N-
(M-biphenyl) -N-phenyl-4'-aminobiphenyl) N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (TPD) was deposited at a deposition rate of 2 nm / se.
The film was deposited to a thickness of 20 nm at c to form a hole transport layer.

Next, the following compound DCM and Tris (8
-Quinolinolato) aluminum (A1Q3) at a weight ratio of 2: 100 and 50 nm at a deposition rate of 0.5 nm / sec.
To form a light emitting layer.

[0104]

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Next, while maintaining the reduced pressure, tris (8-quinolinolato) aluminum was deposited as an electron injecting and transporting layer to a thickness of 10 nm at a deposition rate of 0.2 nm / sec.

Further, while maintaining the reduced pressure state, the MgAg
(Weight ratio 10: 1) at a deposition rate of 0.2 nm / sec.
A cathode was formed by vapor deposition to a thickness of nm to obtain an EL device.

When a voltage was applied to this EL element to cause a current to flow, a red-orange color of 1500 cd / m ² at 615 mA / cm ² at 16 V (maximum emission wavelength λ max = 610 nm, chromaticity coordinate x =
0.59, y = 0.38) was confirmed. The half life of the luminance was 200 hours at a constant current drive of 10 mA / cm ² .

[0108]

As described above, it is apparent that the organic EL device using the coumarin derivative of the formula (I) of the present invention is a highly reliable device that can emit red light with high luminance and can emit light continuously. is there.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of an organic EL device of the present invention.

[Description of Signs] 1 EL element 2 substrate 3 anode 4 hole injection / transport layer 5 light emitting layer 6 electron injection / transport layer 7 cathode 8 color filter film 9 fluorescence conversion filter film 10 sealing layer 11 casing 12 gas or liquid

Claims (7)

[Claims] Claims: 1. It has at least one organic compound layer,
An organic EL device in which at least one organic compound layer contains a coumarin derivative represented by the following formula (I). Embedded image [In the formula (I), R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom or an alkyl group, which may be the same or different. Z represents an atomic group necessary for forming a benzene ring or a naphthalene ring together with two carbon atoms. ] 2. The organic EL device according to claim 1, wherein the organic compound layer containing the coumarin derivative is a light emitting layer. 3. The organic EL device according to claim 2, wherein the coumarin derivative is doped in a host material. 4. The organic EL device according to claim 3, wherein said host material is a quinolinonato metal complex. 5. The organic EL device according to claim 2, wherein the light emitting layer is a mixed layer of at least one kind of hole injecting and transporting compound and at least one kind of electron injecting and transporting compound. 6. The light-emitting layer is sandwiched between at least one hole-injecting and / or hole-transporting layer and at least one electron-injecting and / or electron-transporting layer. An organic EL device according to any one of 2 to 5. 7. The organic electroluminescent device according to claim 1, wherein a color filter and / or a fluorescence conversion filter are arranged on the light extraction side, and light is extracted through the color filter and / or the fluorescence conversion filter.
L element.